The present invention relates to a copier, facsimile transceiver, laser printer or similar image forming equipment and, more particularly, to a control device for such image forming equipment.
It is a common practice with image forming equipment, e.g., a copier to implement a control device as a single control board including a driver and carrying a CPU (Central Processing Unit) thereon. A current trend in the imaging art is toward image forming multifunction equipment and, therefore, toward a control device using a number of CPUs for high-speed processing. Typically, a control device for multifunction equipment is made up of an operating unit for controlling an LCD (Liquid Crystal Display) or similar display and key inputs, a main control unit controlling jam detection and all the peripheral devices and image forming procedure, and a slave control unit for mainly controlling chargers, optics and other image forming devices arranged around a photoconductive element. These three control units have respective CPUs which communicate with one another for controlling the entire equipment.
Specifically, the main control unit has a ROM (Read Only Memory) storing image formation control programs for main control while the slave control unit has a ROM storing image formation control programs for slave control. During image formation, a required control procedure is executed on the basis of the information stored in the ROMs. Necessary data except for the programs are interchanged via interfaces. Image forming equipment of the type including a fixing heater may be operated by a control device in which a plurality of control units have respective CPUs which are capable of communicating with one another.
The programs stored in the ROMs of the control units are not lost even when the power source of the equipment is turned off. However, to change the programs, it is necessary to replace the ROMs. The problem with the conventional control device is that the replacement of the ROM included in the slave control unit is time-consuming since it is positioned at the side or the rear of the equipment. During the replacement of the ROM, the operation of the equipment has to be entirely interrupted, sacrificing the efficiecy.